I used a box cutter and then dremel/sandpaper on mine. Just make sure to get as much out as possible. Then wash the box thoroughly and leave it to dry completely. You don't want any leftover pieces making a trip through the engine.

This exhaust is soo worth it. I picked one up yesterday after my preorder in July and got a free install. Along with that free install, my boy Andrew from active hooked it up by upgrading my stage 1 tune to a stage 2 tune. I highly recommend this exhaust along with literally anything else you can find that active makes.